Analysis of the lattice thermal resistivity due to the presence of electrons at low temperatures: Application to phosphorus-doped Ge

The temperature-dependence of the extra lattice thermal resistivity of a doped sample due to the presence of electrons has been studied at low temperatures for the first time by analysing the extra lattice thermal resistivity due to electrons of five samples of phosphorus-doped Ge having different carrier concentrations in the range 1.2×10²³–1.1×10²⁴ m^?3 in the temperature range 1–5 K. The variation of the extra lattice thermal resistivity of a doped sample due to electrons with the parameters η^* (the reduced Fermi energy),m ^* (the density of states effective mass),E _D (the deformation potential constant) andn (the carrier concentration) which are responsible for the electron-phonon scattering relaxation rate has also been analysed for the first time in the present study. A distinction has been made between non-peripheral and peripheral phonons in the present analysis. An analytical expression is reported for calculation of an approximate value of the extra lattice thermal resistivity of a doped sample due to the presence of electrons at low temperatures.     

Preparation and physico-chemical characterisation of iron(III) complexes containing substituted benzimidazole and Schiff base moieties

New complexes of iron(III) of the type [(μ-Cl)₂Fe₂{η ²-(opbz)₄] (1) and [(Cl)₂Fe{η ²-(opbz)] (2) [Hopbz = {2-(o-hydroxyphenyl)}-benzimidazole, η ² = Number of connectivity sites involved in bonding the metal] have been synthesized by the interactions of iron(III) chloride with the corresponding ligand (Hopbz) in 1:2 and 1:1 molar ratio(s) in hot EtOH. The complex (1) was further treated with various sodium salts of Schiff bases (sb) [Na(o-smab), Na(p-smab) and Na(sap)], alkoxo-Na(OPrⁱ), aryloxo-Na(OAr) and tetraisopropoxyaluminate [Na{Al(OPrⁱ)₄] in a 1:1 molar ratio (in THF–benzene medium) to produce derivatives of the type: {(η ²-(sb) Fe{η ²-opbz)₂] (3), (4) and (5), [(μ-OPrⁱ)₂Fe₂{η-(opbz)₄}] (6) [(μ-OAr)₂Fe₂{η-(opbz)₄}] (7) and [(μ-OPrⁱ)₂Al(OPrⁱ)₂-Fe{η-(opbz)₂}] (8). All these derivatives were characterised by elemental analysis, spectral (IR, UV–visible and FAB-mass) and magnetic susceptibility measurements. On the basis of these studies, a distorted octahedral (dimeric) geometry around iron(III) for the complexes (1), (6), (7) and (8) have been suggested.     

Polyimide-epoxy alloys prepared via micro-modification: Water sorption and diffusion

A novel polyimide-epoxy or PI-EP alloys are prepared by the modification of polyamic acid in the concentration range of 1.54×10⁻⁶ to 1.54×10⁻² mol/L. The methanol sorption for these alloys at 24 hrs and at equilibrium conditions are determined and the residual solvent in fully cyclized polyimides were calculated. The presence of the residual solvent is visualized in fully imidized polymer and a structure containing partly imidized amic acid moiety is proposed and their concentration (in percentage) is calculated. The water sorption for these alloys at 24 hrs and at equilibrium conditions and the values of the water diffusion coefficient are determined from absorption isotherms. The PI-EP alloys have shown comparatively lower water sorption and higher diffusion coefficient than the unmodified polyimide. The mechanistic aspects of water sorption and diffusion are discussed.     

16‐(4‐Cyano­benzyl­idene)‐17‐oxo­androst‐5‐en‐3β‐ol

In the title compound, 4‐(3β‐hydroxy‐17‐oxoandrost‐5‐en‐16‐ylidenemethyl)benzonitrile, C₂₇H₃₁NO₂, rings A and C of the steroid nucleus are in chair conformations. The central six‐membered ring B is in an 8β,9α‐half‐chair conformation, while the five‐membered ring D adopts a 13β,14α‐half‐chair conformation. The cyano­benzyl­idene moiety has an E configuration with respect to the carbonyl group at position C17. The dihedral angle between the planes of the steroid nucleus and the cyano­benzyl­idene moiety is 22.61 (15)°. Intermolecular O—H⃛N hydrogen bonds formed between the hydroxyl group of the steroid and the N atom of the cyano­benzyl­idene moiety of symmetry‐related mol­ecules link the steroid mol­ecules into chains which run parallel to the b axis.     

Role of oxygen and carbon on donor formation in step-annealed CZ-silicon

Step-annealing schedules for two different annealing chains, i.e. 450-650-450 and 650-450-700 °C have been followed to study the effect of oxygen and carbon on donor formation in carbon-rich Czochralski-silicon. It has been found that the annealing time does not have reasonable effect on substitutional carbon atoms. On the other hand, interstitial oxygen atoms are drastically reduced depending on annealing temperature. Carbon concentration does not exhibit any relationship with new donor (ND) concentration. The result suggests that the ND formation is not controlled by the substitutional carbon concentration directly, but by a density of some unknown embryos. The energy of formation of NDs was found to be 1.84 eV. All these results with plausible explanation are reported here.     

Composite high resolution localized relaxation scheme based on upwinding for hyperbolic conservation laws

In this work we present an upwind‐based high resolution scheme using flux limiters. Based on the direction of flow we choose the smoothness parameter in such a way that it leads to a truly upwind scheme without losing total variation diminishing (TVD) property for hyperbolic linear systems where characteristic values can be of either sign. Here we present and justify the choice of smoothness parameters. The numerical flux function of a high resolution scheme is constructed using wave speed splitting so that it results into a scheme that truly respects the physical hyperbolicity property. Bounds are given for limiter functions to satisfy TVD property. The proposed scheme is extended for non‐linear problems by using the framework of relaxation system that converts a non‐linear conservation law into a system of linear convection equations with a non‐linear source term. The characteristic speed of relaxation system is chosen locally on three point stencil of grid. This obtained relaxation system is solved using composite scheme technique, i.e. using a combination of proposed scheme with the conservative non‐standard finite difference scheme. Presented numerical results show higher resolution near discontinuity without introducing spurious oscillations. Copyright © 2008 John Wiley & Sons, Ltd.     

Electroluminescence in the phosphor anthracene doped by 9-vinylanthracene

Electroluminescence has been excited in the phosphor anthracene doped by 9-vinylanthracene (10⁻⁴ mole %) at room temperature (300°K). Variation of light output with voltage is governed by the relationB=B ₀ exp [−(C/V ^1/2)] as in the case of inorganic phosphors. HereB ₀ andC are constants andV is the rms value of the voltage applied to the phosphor. Frequency dependence of the electroluminescence has also been studied at different voltages of the applied electric field.